1. Field of the Invention
The present invention relates to an imaging optical system, a camera apparatus using the imaging optical system, and a personal digital assistant using the camera apparatus.
2. Description of the Related Art
As digital cameras become widely prevalent, a better exterior form and a high performance are envisaged. In particular, further miniaturization of a camera main body is required for a better exterior form, and a higher image quality, a wider angle and a larger caliber able to correspond to an imaging element exceeding ten million pixels are required for a high performance.
A high image quality in the case of a short-distance object, a capability of micro photographing, and energy-saving properties also are required.
An imaging optical system that moves a plurality of lens groups when “focusing from an infinity-distance object to a short-distance object” is disclosed in, for example, Japanese Patent Publication No. 2005-292344, Japanese Patent Publication No. 2005-257912, Japanese Patent No. 3607958, and Japanese Patent No. 3352264.
A structure in which three lens groups including a lens group fixed at the time of focusing and two focusing lens groups that move for focusing are disposed in an image side, in other words, a side focusing an image of an aperture stop is disclosed in Japanese Patent Publication No. 2005-292344. However, in the structure, an F number is 2.1 or more.
On the other hand, in the imaging optical systems disclosed by Japanese Patent Publication No. 2005-257912, Japanese Patent No. 3607958, and Japanese Patent. No. 3352264, an aperture stop is moved at the time of focusing.